The employment of conveyor belts and endless conveyor belts for moving bulk materials has been known for almost two centuries. Belting systems have been used for conveying materials distances ranging from several yards to many miles. The selection of any haulage system generally depends upon the economics of the situation and the specific material being conveyed. The employment of endless belt conveyor systems have proven economically efficacious in the conveyance of raw materials including coal from the point they are mined to a tipple point removed therefrom. One reason for this is the convenience afforded by portable belt systems which may be added to existing conveyor systems to extend them into newly opened areas of the mine as work progresses.
While endless belt conveying systems have been successfully employed in the handling of raw materials, and especially coal, recent developments in mining safety and in mining as well as belting economics have dictated increased efficiency and safety within the mine. One specific area which has caused a relatively large amount of manpower utilization, safety controversy, and belt wear relates directly to the small particles or fines which are formed when various conglomerate raw materials such as coal are mined and hauled, and which are undesirably retained on the belt subsequent to the dumping of the material being conveyed.
The fines associated with coal conveying have created problems for the last 25 years ranging from belt wear to the requirement that workmen be employed to patrol the length of the belt and shovel back the fines which fall from the belt on its return travel path and build up under the belt. One area which has caused difficulties, relative to efficient belt conveying, concerns the build-up of the fines around and upon the idler rollers which lie below the belt and support the same on its return trip from the belt head, where the material is dumped off the belt, to the tail end, where the material being conveyed is loaded upon the belt. This is especially troublesome when considered in light of the fact that MESA requirements regarding coal dust in mines require water wetting of the belt at the dumping end of the belt, thereby increasing fine build-up along the entire belt. This increased material wetness leads, in almost every circumstance found, to increased fine adhesion to the belt and, consequently, to fine build-up in greater proportions than that realized under "dry" conditions. Fine build-up at these points causes the clogging of the idler rollers which may in turn affect the manner in which the conveyor belt tracks upon the idler rollers. Additionally, fine build-up causes increased friction in the idler roller which results in increased belt wear and possible premature belt wearout or the idler sawing through the belt.
As noted above, the present method of operation is to continue to manually return the fines which fall from the belt during the belt's movement toward the tipple point. This method requires the additional cost of manual labor as well as the very important possibility, which has occurred in the past, that workmen may be harmed or killed in the process. In addition to causing possible injury, belt maintenance is drastically increased when the fines are not removed from the belt as its head end along with the load being conveyed. In particular, maintenance includes belt splicing subsequent to breakage, idler replacement due to increased frictional wearing, rapid corrosive deterioration of the entire belt system and adjacent structures, bearing failure and belt replacement. The latter may be exceedingly expensive in the longer belt systems, costing a minimum of five dollars a foot per 36-inch wide belts for the least expensive variety, and running higher for rubber belts. Consequently, it becomes extremely important to minimize, if not completely eliminate, the build-up of fines under the belt after the belt changes direction and begins its return to the loading point.
The solutions to fine build-up along the return path of the belt are as numerous as the number of belts in use. They have one common area however, and that is their ineffectuality in removing a meaningful percentage of the fines from the conveyor belt. Wipers and scrapers of various configurations and materials have been employed, and are currently employed, in an attempt to remove fines from the belt. Such methods, in addition to being ineffective, cause undesirable increased belt wear and increased costs in their replacement. Washing the belt with plain water has been attempted, but has been generally done away with as causing flooding within the mine area as well as causing the belt to freeze in winter conditions. Moreover, belt washing has been found to be ineffective in reducing fine build-up. Excess water shortens belt life, creates corrosion, and promotes pollution. Brushes, both rotating and stationary, have been used to reduce fine carryover past the head end of the belt. While these attempts have met with limited success in reducing fine carryover, they require enormous amounts of maintenance in order to retain their rather limited effectiveness. Additionally, brushes, because of their necessary contact with the conveyor belt, cause excessive belt wear and generally clog up when used to move wet materials such as coal. Lastly, twisted belt drives have been employed and are characterized in having two 180 degree twists in the belt's path of travel between the head end and the tail end. Such adaptations have limited efficacy in many applications, the least of which is coal mining. In addition, twisted belt drive systems require maintenance, are relatively difficult to operate in confined areas, and are limited to longer belts.
The problem of fines, as suggested above, is not new. Attempts to solve the problem have been prevalent for the last quarter century and have been generally unsuccessful. The problem of fines and a relatively maintenance-free and efficient method for their removal has continued to plague coal operators, as well as those of any raw materials having associated fines. Some of the procedures employed are evidenced in issued U.S. patents as well as foreign patents. Among these are:
1. Hogg, U.S. Pat. No. 3,529,868; PA1 2. Forby et al, U.S. Pat. No. 1,832,374; PA1 3. Bonnet, U.S. Pat. No. 2,478,230; and PA1 East German Pat. to Nikol et al, Pat. No. 26,225
The first three of these have been the subject of previous prosecution relative to the parent of this application. All, however, fail to teach or show anything more (relative to fine reduction) than the use of silicone oils as release agents, something known for many years. Thus, they are all directed to the solution of problems independent of the one under consideration here, i.e., what application rates produce the greatest amount of fine release.